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Abstract: We investigate the effects of ZnO annealing temperature (T A ) on the performance of inverted polymer solar cells with ZnO electron-selective layers deposited by spin coating aqueous solutions of an ammine-hydroxo zinc complex. The inverted solar cells based on poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester with T A as low as 80°C exhibit power-conversion efficiencies of 3.6%, which is equal to those of devices with higher T A . Characterizations of the ZnO films using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, grazing incidence wide-angle X-ray scattering, and optical transmittance measurements show that the abrupt improvement of device performance from T A =60 to 80°C is due to the improvement of energy-level alignment arising from the increases in the relative amount and the crystallinity of ZnO. [Copyright &y& Elsevier]

Abstract: Transparent super-hydrophobic films were fabricated using the PDMS method and silane process, based on anodization in phosphoric acid. Contact angle tests were performed to determine the contact angle of each film according to the anodizing time. Transmittance tests also were performed to obtain the transparency of each TPT (trimethylolpropane propoxylate triacrylate) replica film according to the anodizing time. The contact angle was determined by studying the drop shape, and the transmittance was measured using a UV-spectrometer. The contact angle increases with increasing anodizing time, because increasing pillar length can trap more air between the TPT replica film and a drop of water. The transmittance falls with increasing anodizing time because the increasing pillar length causes a scattering effect. This study shows that the pillar length and transparency are inversely proportional. The TPT replica film having nanofibers array structures was better than other films in aspect of self-cleaning by doing quantitative experimentation. [Copyright &y& Elsevier]

Abstract: The sequence with which the polymer photoactive layer is annealed during inverted solar cell fabrication not only affects device characterization, it also influences the stability of devices dramatically. Devices in which the photoactive layer is annealed after top electrode deposition outlast devices in which the photoactive layer is annealed before top electrode deposition. This difference in device stability is traced to the grain structure and grain size of the top electrode, which in turn shows strong dependence on the underlying morphology of the photoactive layer. Annealing the photoactive layer causes significant roughening of the film; subsequent metal deposition results in electrodes with small grains. It is moisture penetration through the grain boundaries of the metal electrode that results in the deterioration of photovoltaic characteristics in devices in which the photoactive layer is annealed before top electrode deposition. [Copyright &y& Elsevier]

Abstract: We demonstrate here with the feasibility of superporous agarose (SA) beads as a solid support in microfluidic immunoassay by detecting goat IgG. In our procedure, SA beads containing superpores were covalently conjugated to protein A. The conjugated beads were introduced into a polydimethyl siloxane microfluidic device. The sandwich immunoassay was performed in the microfluidic device by subsequently introducing anti-goat IgG as the primary antibodies, goat IgG as analytes, alkaline phosphatase-conjugated F(ab′)2 anti-goat IgG as detection antibodies, and 5-bromo-4-chloro-3-indolylphosphate/nitroblue tetrazolium as substrate in a flow. Depending on the goat IgG concentration, dark and pinky precipitates appeared inside the microchannel immediately after the introduction of all the reagents. The minimum detection limit, 100pg goat IgG/mL in PBS, was achieved with the naked eye. This enhanced sensitivity is mainly because analytical reagents were allowed to access the outer surface as well as the inner matrices of the beads. This is supported by the facts that the binding of fluorescein isothiocyanate IgG happened throughout the inside matrices of protein A-conjugated SA beads but was limited to the outer surface of protein A-conjugated homogeneous agarose beads. These results suggest that SA beads are highly suitable as a solid support for microfluidic immunoassays. [Copyright &y& Elsevier]

Abstract: Mononuclear nonheme oxoiron(IV) complexes bearing 15-membered macrocyclic ligands were generated from the reactions of their corresponding iron(II) complexes and iodosylbenzene (PhIO) in CH3CN. The oxoiron(IV) species were characterized with various spectroscopic techniques such as UV–vis spectrophotometer, electron paramagnetic resonance, electrospray ionization mass spectrometer, and resonance Raman spectroscopy. The oxoiron(IV) complexes were inactive in olefin epoxidation. In contrast, when iron(II) or oxoiron(IV) complexes were combined with PhIO in the presence of olefins, high yields of epoxide products were obtained. These results indicate that in addition to the oxoiron(IV) species, there must be at least one more active oxidant (e.g., FeIV-OIPh adduct or oxoiron(V) species) that effects the olefin epoxidation. We have also demonstrated that the ligand environment of iron catalysts is an important factor in controlling the catalytic activity as well as the product selectivity in the epoxidation of olefins by PhIO. [Copyright &y& Elsevier]

Two lanthanum hydroxide (LH, La(OH) 3) materials, i.e., La(OH) 3 submicroplates (LHSMPs) and La(OH) 3 nanoparticles (LHNPs), were synthesized hydrothermally, and their optical and encapsulation properties were investigated. The surfaces of the LHSMPs and the LHNPs were modified with a coupling agent: [3-(methacryloyloxy)propyl] trimethoxysilane (MPS). To prepare transparent encapsulation composite materials, both types of surface-modified particles were dispersed in a poly(urethane acrylate) (PUA) adhesive polymer binder. The composite film with surface-modified LHNP-PUA exhibited better optical properties (higher transmittance and lower haze) than that with surface-modified LHSMP-PUA owing to smaller particle size. However, the latter was observed to be more advantageous for preventing the permeation of water molecules owing to the larger particle size. Image 1 • La(OH) 3 submicroplates (LHSMPs) and La(OH) 3 nanoparticles (LHNPs) are synthesized by a hydrothermal method. • The surfaces of particles are modified by MPS. • LHNPs exhibited higher transmittance and lower haze than LHSMPs owing to the smaller particle size. • LHSMPs exhibited better encapsulation properties against water permeation than LHNPs owing to the larger particle size. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs), favored for their high energy density, have slow charging issues due to redox reactions in both electrodes. To overcome these issues, we present a hybrid energy storage system that delivers high energy density without sacrificing power density. This hybrid system is made up of an expanded graphite/copper oxide composite as the anode material and a porous carbon as the positive electrode material. The proposed composite anode is fabricated in one step; it shows a high specific capacity and a high specific power density due to a lowered lithium -ion insertion barrier of expanded graphite derived from copper oxide synthesis and pre-lithiation. The high theoretical capacity of copper oxide is effective in yielding high energy density. Furthermore, the reaction kinetic balancing needed for a lithium-ion capacitor is determined by the mass ratio of its electrodes. As a result, it is confirmed that internal resistance is more important than specific capacity for a lithium-ion capacitor, unlike a Li-ion battery. The optimized hybrid cell shows a high specific energy density of 212.3 Wh kg−1 at a specific power density of 1.3 kW kg−1 and maintains 85% of its initial energy density after 500 cycles. • Balancing the reaction kinetics between the GCuO electrode and the PC electrode was studied. • The relationship internal resistance and pre-lithiation was investigated. • Proposed LICs showed high energy density of 212.3 Wh kg−1 at a specific power density of 1.3 kW kg−1. [ABSTRACT FROM AUTHOR]

Transparent encapsulation materials were fabricated by combining inorganic mesoporous silica nanoparticles (MSNPs) and a transparent polyurethane acrylate (PUA)-based resin. The surfaces of the synthesized MSNPs were successfully modified by a two-step sol-gel method with the coupling agent [3-(methacryloyloxy)propyl]trimethoxysilane (MPS). The bare and MPS-modified MSNPs possessed good hygroscopic properties (20% and 17%, respectively). The optimized MSNP-PUA composite containing 2 wt% MPS-modified MSNPs exhibited a high transparency (94.8%) with low haze (2.1%) and excellent encapsulation properties (lasted 576 h in a moisture permeability test at 85 °C and 85% RH). Image 1 • Mesoporous silica nanoparticles (MSNPs) are successfully synthesized by a hydrothermal method. • The surface of MSNPs is successfully modified by MPS. • Hygroscopic MPS-modified MSNPs are uniformly dispersed in polyurethane acrylate resin. • The fabricated MSNP-PUA composites are optically transparent and possess excellent encapsulation properties. [ABSTRACT FROM AUTHOR]

The formation of a stable solid electrolyte interphase (SEI) layer is crucial for enhancing the safety and lifespan of Li metal batteries. Fundamentally, a homogeneous Li + behavior by controlling the chemical reaction at the anode/electrolyte interface is the key to establishing a stable SEI layer. However, due to the highly reactive nature of Li metal anodes (LMAs), controlling the movement of Li + at the anode/electrolyte interface remains challenging. Here, an advanced approach is proposed for coating a sacrificial layer called fluorinated self-assembled monolayer (FSL) on a boehmite-coated polyethylene (BPE) separator to form a stable SEI layer. By leveraging the strong affinity between the fluorine functional group and Li + , the rapid formation of a LiF-rich SEI layer in the cell production and early cycling stage is facilitated. This initial stable SEI formation promotes the subsequent homogeneous Li + flux, thereby improving the LMA stability and yielding an enhanced battery lifespan. Further, the mechanism behind the stable SEI layer generation by controlling the Li + dynamics through the FSL-treated BPE separator is comprehensively verified. Overall, this research offers significant contributions to the energy storage field by addressing challenges associated with LMAs, thus highlighting the importance of interfacial control in achieving a stable SEI layer., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

Electrolyte-gated transistors (EGTs) are promising candidates as artificial synapses owing to their precise conductance controllability, quick response times, and especially their low operating voltages resulting from ion-assisted signal transmission. However, it is still vague how ion-related physiochemical elements and working mechanisms impact synaptic performance. Here, to address the unclear correlations, we suggest a methodical approach based on electrochemical analysis using poly(ethylene oxide) EGTs with three alkali ions: Li + , Na + , and K + . Cyclic voltammetry is employed to identify the kind of electrochemical reactions taking place at the channel/electrolyte interface, which determines the nonvolatile memory functionality of the EGTs. Additionally, using electrochemical impedance spectroscopy and qualitative analysis of electrolytes, we confirm that the intrinsic properties of electrolytes (such as crystallinity, solubility, and ion conductivity) and ion dynamics ultimately define the linearity/symmetricity of conductance modulation. Through simple but systematic electrochemical analysis, these results offer useful insights for the selection of components for high-performing artificial synapses.

Multivalued logic (MVL) technology is a promising solution for improving data density and reducing power consumption in comparison to complementary metal-oxide-semiconductor (CMOS) technology. Currently, heterojunction transistors (TRs) with negative differential transconductance (NDT) characteristics, which play an important role in the function of MVL circuits, adopt organic or 2D semiconductors as active layers, but it is still difficult to apply conventional CMOS processes. Herein, we demonstrate an oxide semiconductor (OS) heterojunction TR with NDT characteristics composed of p-type copper(I) oxide (Cu 2 O) and n-type indium gallium zinc oxide (IGZO) using the conventional CMOS manufacturing processes. The electrical characteristics of the fabricated device exhibit a high I on / I off ratio (∼3 × 10 3 ), wide NDT ranges (∼29 V), and high peak-to-valley current ratios (PVCR ≈ 25). The electrical properties of 15 devices were measured, confirming uniform performance in the PVCR, NDT range, and I on / I off ratio. We analyze the device operation by varying the source/drain (S/D) position and changing the device geometry and the thickness of the Cu 2 O layer. Additionally, we demonstrate heterojunction ambipolar TR to elucidate the transport mechanism of NDT devices at a high gate voltage ( V GS ). To confirm the feasibility of the MVL circuit, we present a ternary inverter with three clearly expressed logic states that have a long intermediate state and greater margin of error induced by wide NDT regions and high PVCR.

Recently, two-dimensional transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS 2 ) have attracted great attention due to their unique properties. To modulate the electronic properties and structure of TMDs, it is crucial to precisely control chalcogenide vacancies and several methods have already been suggested. However, they have several limitations such as plasma damage by ion bombardment. Herein, we introduced a novel solvent-assisted vacancy engineering (SAVE) method to modulate sulfur vacancies in MoS 2 . Considering polarity and the Hansen solubility parameter (HSP), three solvents were selected. Sulfur vacancies can be modulated by immersing MoS 2 in each solvent, supported by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses. The SAVE method can further expand its application in memory devices representing memristive performance and synaptic behaviors. We represented the charge transport mechanism of sulfur vacancy migration in MoS 2 . The non-destructive, scalable, and novel SAVE method controlling sulfur vacancies is expected to be a guideline for constructing a vacancy engineering system of TMDs.

Composite solid electrolytes (CSEs) are newly emerging components for all-solid-state Li-metal batteries owing to their excellent processability and compatibility with the electrodes. Moreover, the ionic conductivity of the CSEs is one order of magnitude higher than the solid polymer electrolytes (SPEs) by incorporation of inorganic fillers into SPEs. However, their advancement has come to a standstill owing to unclear Li-ion conduction mechanism and pathway. Herein, the dominating effect of the oxygen vacancy (O vac ) in the inorganic filler on the ionic conductivity of CSEs is demonstrated via Li-ion-conducting percolation network model. Based on density functional theory, indium tin oxide nanoparticles (ITO NPs) are selected as inorganic filler to determine the effect of O vac on the ionic conductivity of the CSEs. Owing to the fast Li-ion conduction through the O vac inducing percolation network on ITO NP-polymer interface, LiFePO 4 /CSE/Li cells using CSEs exhibit a remarkable capacity in long-term cycling (154 mAh g -1 at 0.5C after 700 cycles). Moreover, by modifying the O vac concentration of ITO NPs via UV-ozone oxygen-vacancy modification, the ionic conductivity dependence of the CSEs on the surface O vac from the inorganic filler is directly verified., (© 2023 Wiley-VCH GmbH.)

Recently, several studies have revealed that the thermal annealing process induces intermixing at the interfaces of multilayered solution-processed organic light emitting diodes (OLEDs) and enhances their device performance. Depth profiling measurements, such as neutron reflectometry, have meticulously shown that significant intermixing occurs when the annealing temperature exceeds the glass transition temperature ( T g ) of OLED materials. However, electrical characterization to unveil the physical origins of the correlation between interfacial characteristics and device performance is still lacking. Here, we introduce impedance spectroscopy (IS) analysis to examine the thermally induced modifications of charge carrier dynamics in a solution-processed bilayer OLED, consisting of an emission layer and an electron transporting layer (ETL). The characteristic relaxation frequency and capacitance extracted from the capacitance-frequency spectra of the OLEDs thermally annealed at varying temperatures were utilized to separately assess the conductance of the ETL and interfacial carrier accumulation, respectively. The results show that the improved charge transport of the ETL upon thermal annealing is mainly responsible for the performance enhancement since annealing the OLEDs at a temperature above the T g of the ETL, at which significant intermixing occurs, promotes non-radiative trap-assisted recombination and thereby deteriorates the current efficiency. The proposed IS analysis exhibits that IS can separately probe the charge transport, interfacial charge accumulation and recombination process which are crucial for accurate analysis of charge carrier dynamics in solution-processed OLEDs and can thus be utilized to identify the key factors limiting the device performance.

Oxide thin-film transistors (TFTs) have attracted much attention because they can be applied to flexible and large-scaled switching devices. Especially, oxide semiconductors (OSs) have been developed as active layers of TFTs. Among them, indium-gallium-zinc oxide (IGZO) is actively used in the organic light-emitting diode display field. However, despite their superior off-state properties, IGZO TFTs are limited by low field-effect mobility, which critically affects display resolution and power consumption. Herein, we determine new working mechanisms in dual-stacked OS, and based on this, we develop a dual-stacked OS-based TFT with improved performance: high field-effect mobility (∼80 cm 2 /V·s), ideal threshold voltage near 0 V, high on-off current ratio (>10 9 ), and good stability at bias stress. Induced areas are formed at the interface by the band offset: band offset-induced area (BOIA) and BOIA-induced area (BIA). They connect the gate bias-induced area (GBIA) and electrode bias-induced area (EBIA), resulting in high current flow. Equivalent circuit modeling and the transmission line method are also introduced for more precise verification. By verifying current change with gate voltage in the single OS layer, the current flowing direction in the dual-stacked OS is calculated and estimated. This is powerful evidence to understand the conduction mechanism in a dual-stacked OS-based TFT, and it will provide new design rules for high-performance OS-based TFTs.

Water-infiltration-induced power generation has the renewable characteristic of generating electrical energy from ambient water. Importantly, it is found that the carrier concentration in semiconductor constituting the energy generator seriously affect the electricity generation. Nevertheless, few studies are conducted on the influence of semiconductor carrier concentration, a crucial factor on electricity generation. Due to this, understanding of the energy harvesting mechanism is still insufficient. Herein, the semiconductor carrier concentration-dependent behavior in water-infiltration-induced electricity generation and the energy harvesting mechanism by ionovoltaic effect are comprehensively verified. A clue to enhance the electric power generation efficiency is also proposed. When 20 µL of water (NaCl, 0.1 m) infiltrates into a porous CuO nanowires film (PCNF), electric power of ≈0.5 V and ≈1 µA are produced for 25 min. Moreover, the PCNF shows good practicability by generating electricity using various ambient water, turning on LEDs, and being fabricated as a curved one., (© 2021 Wiley-VCH GmbH.)

The change in electrical properties of electrodes by adsorption or desorption at interfaces is a well-known phenomenon required for signal production in electrically transduced sensing technologies. Furthermore, in terms of electrolyte-insulator-semiconductor (EIS) structure, several studies of energy conversion techniques focused on ion-adsorption at the solid-liquid interface have suggested that the electric signal is generated by ionovoltaic phenomena. However, finding substantial clues for the ion-adsorption phenomena in the EIS structure is still a difficult task because direct evidence for carrier accumulation in semiconductors by Coulomb interactions is insufficient. Here, a sophisticated Hall measurement system is demonstrated to quantitatively analyze accumulated electron density-change inside the semiconductor depending on the ion-adsorption at the solid-liquid interface. Also, an enhanced EIS-structured device is designed in an aqueous-soaked system that works with the ionovoltaic principle to monitor the ion-dynamics in liquid electrolyte media, interestingly confirming ion-concentration dependence and ion-specificity by generated peak voltages. This newly introduced peculiar method contributes to an in-depth understanding of the ionovoltaic phenomena in terms of carrier actions in the semiconductors and ionic behaviors in the aqueous-bulk phases, providing informative analysis about interfacial adsorptions that can expand the scope of ion-sensing platforms., (© 2021 Wiley-VCH GmbH.)

Metal oxide semiconductors doped with additional inorganic cations have insufficient electron mobility for next-generation electronic devices so strategies to realize the semiconductors exhibiting stability and high performance are required. To overcome the limitations of conventional inorganic cation doping to improve the electrical characteristics and stability of metal oxide semiconductors, we propose solution-processed high-performance metal oxide thin-film transistors (TFTs) by incorporating polyaniline (PANI), a conductive polymer, in a metal oxide matrix. The chemical interaction between the metal oxide and PANI demonstrated that the defect sites and crystallinity of the semiconductor layer are controllable. In addition, the change in oxygen-related chemical bonding of PANI-doped indium oxide (InO x ) TFTs induces superior electrical characteristics compared to pristine InO x TFTs, even though trace amounts of PANI are doped in the semiconductor. In particular, the average field-effect mobility remarkably enhanced from 15.02 to 26.58 cm 2 V -1 s -1 , the on/off current ratio improved from 10 8 to 10 9 , and the threshold voltage became close to 0 V actually from -7.9 to -1.4 V.

Highly transparent optical logic circuits operated with visible light signals are fabricated using phototransistors with a heterostructure comprised of an oxide semiconductor (ZnO) with a wide bandgap and quantum dots (CdSe/ZnS QDs) with a small bandgap. ZnO serves as a highly transparent active channel, while the QDs absorb visible light and generate photoexcited charge carriers. The induced charge carriers can then be injected into the ZnO conduction band from the QD conduction band, which enables current to flow to activate the phototransistor. The photoexcited charge transfer mechanism is investigated using time-resolved photoluminescence spectroscopy, scanning Kelvin probe microscopy, and ultraviolet photoelectron spectroscopy. Measurements show that carriers in the QD conduction band can transfer to the ZnO conduction band under visible light illumination due to a change in the Fermi energy level. Moreover, the barrier for electron injection into the ZnO conduction band from the QD conduction band is low enough to allow photocurrent generation in the QDs/ZnO phototransistor. Highly transparent NOT, NOR, and NAND optical logic circuits are fabricated using the QDs/ZnO heterostructure and transparent indium tin oxide electrodes. This work provides a means of developing highly transparent optical logic circuits that can operate under illumination with low-energy photons such as those found in visible light., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We present an atmospheric-pressure plasma (APP) treatment technique to improve the electrical performance of solution-processed dielectric films. This technique can successfully reduce leakage current and frequency dependence of solution-processed dielectric films. The APP treatment contributes to the conversion of metal hydroxide to metal oxide, and in the case of a solution-treated AlO x dielectric thin film, it effectively ascribes to the formation of high-quality AlO x dielectric thin films. The capacitance of the untreated AlO x dielectric thin film varies up to 9.9% with frequency change, but the capacitance of the APP treated AlO x dielectric thin film varies within 1.5%. When the solution-processed InO x thin-film transistors (TFTs) were fabricated using these dielectric films, the field-effect mobility of TFTs with the APP-treated AlO x dielectric film was increased significantly from 9.77 to 26.79 cm 2 V -1 s -1 in comparison to that of TFTs with the untreated AlO x dielectric film. We also have confirmed that these results are similar to the properties of the sample prepared at high annealing temperature including electrical performance, conduction mechanism and chemical structure. The APP treatment technique provides a new opportunity to effectively improve the electrical performance of solution-processed dielectrics in the atmosphere at low temperature.

Growing attention has been given to low temperature, solution-processed metal oxide thin-film transistors because they can be applied in the emerging sector of flexible and large-scale electronics. However, major obstacles of solution-grown devices, such as their relatively low field-effect mobility and the difficulty of controlling carrier concentration, limit the further advancement of the electronics. Here, we overcome these constraints through a newly renovated structure, called a "homojunction", consisting of double-stacked semiconductors with same material. The homojunction oxide thin-film transistor has remarkable electrical performance with controllability, for example, tunable turn-on voltage (-80 V to -8 V) and high average field-effect mobility (∼50 cm 2 /V·s) are obtained via a low annealing temperature process (250 °C). Furthermore, notable achievements associated with stability, reliability, and uniformity are verified. These results are attributed to the unique phenomena of solution-grown thin films: the change of both chemical and physical properties of thin films. Our findings highlight that the thin films of high quality can be yielded through the solution process at low annealing temperatures, and thus solution-grown transistors hold great promise for widespread industrial applications.

Solution-processed zirconium oxide (ZrO 2 ) dielectrics were formed via a non-hydrolytic sol-gel route at low-temperature, and are suitable for flexible thin film transistor (TFT) devices. Precursor solutions with equimolar zirconium halide and zirconium alkoxide were prepared, and amorphous ZrO 2 films were obtained by spin-coating and annealing at 300 °C through the direct condensation reaction between them. The ZrO 2 films exhibited a high dielectric constant near 10, and a low leakage current density of 5 × 10 -8 A cm -2 at a field of 1 MV cm -1 . High mobility p-type pentacene TFTs were fabricated using the ZrO 2 dielectrics, with a saturation field-effect mobility of 3.7 cm 2 V -1 s -1 , a threshold voltage of -2.7 V, an on/off ratio of 1.1 × 10 6 and a subthreshold swing of 0.65 V dec -1 ., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Solution-processed oxide semiconductors (OSs) have attracted much attention because they can simply, quickly, and cheaply produce transparent channels on flexible substrates. However, despite such advantages, in the fabrication process of OS thin-film transistors (TFTs) using the solution process, it is a fatal problem that there are hardly any ways to simply and effectively control important TFT parameters, including the turn-on voltage ( V on ) and on/off current ratio. For the practical application of solution-processed OS TFT, approaches to simply and effectively control the parameters are urgently required. Here, we newly propose an atmospheric-pressure plasma (APP) treatment that can simply and effectively control the electrical properties in solution-processed InO x TFTs. Through exposure of APP, we successfully realized the changes in important TFT parameters of solution-processed InO x TFT, V on from -11.4 to -1.9 V and the on/off current ratio from ∼10 3 to ∼10 6 , which still keep up the high field-effect mobility (>20 cm 2 V -1 s -1 ). On the basis of various analyses such as X-ray-based analysis and UV-visible spectroscopy, we identified that the APP treatment can effectively control oxygen vacancy and carrier concentration in solution-processed OS.

In this study, we developed a roll-to-roll Ag electroplating process for metallic nanowire electrodes using a galvanostatic mode. Electroplating is a low-cost and facile method for deposition of metal onto a target surface with precise control of both the composition and the thickness. Metallic nanowire networks [silver nanowires (AgNWs) and copper nanowires (CuNWs)] coated onto a polyethylene terephthalate (PET) film were immersed directly in an electroplating bath containing AgNO 3 . Solvated silver ions (Ag + ions) were deposited onto the nanowire surface through application of a constant current via an external circuit between the nanowire networks (cathode) and a Ag plate (anode). The amount of electroplated Ag was systematically controlled by changing both the applied current density and the electroplating time, which enabled precise control of the sheet resistance and optical transmittance of the metallic nanowire networks. The optimized Ag-electroplated AgNW (Ag-AgNW) films exhibited a sheet resistance of ∼19 Ω/sq at an optical transmittance of 90% (550 nm). A transmission electron microscopy study confirmed that Ag grew epitaxially on the AgNW surface, but a polycrystalline Ag structure was formed on the CuNW surface. The Ag-electroplated metallic nanowire electrodes were successfully applied to various electronic devices such as organic light-emitting diodes, triboelectric nanogenerators, and a resistive touch panel. The proposed roll-to-roll Ag electroplating process provides a simple, low-cost, and scalable method for the fabrication of enhanced transparent conductive electrode materials for next-generation electronic devices.

The technology for electrical current passing through an insulator thin-film between two electrodes is newly getting spotlights for substantial potentials toward advanced functional devices including a diode and a resistive switching device. However, depending on an electrode-limited conduction mechanisms of the conventional devices, a narrow processing window for a thickness of the insulator thin-film and an inability to control a magnitude and direction of the currents are challenges to overcome. Herein, we report a new approach to enable electrical charge carriers to pass stably through a relatively-thick insulator layer and to control a magnitude and polarity of the currents by applying an oxide semiconductor electrode in a metal/insulator/metal structure. We reveal that the electrical conduction in our devices follows a space charge-limited conduction mechanism which mainly depends on the charge carriers injected from contacts. Therefore, characteristics of the current including a current value and a rectification ratio of input signal are precisely controlled by electrical properties of the oxide semiconductor electrode. The unique current characteristics in metal/insulator/oxide semiconductor structures give extendable inspirations in electronic materials science, even a prominent solution for various technology areas of electronics.

Due to its extreme thinness, graphene can transmit some surface properties of its underlying substrate, a phenomenon referred to as graphene transparency. Here we demonstrate the application of the transparency of graphene as a protector of thin-film catalysts and a booster of their catalytic efficiency. The photocatalytic degradation of dye molecules by ZnO thin films was chosen as a model system. A ZnO thin film coated with monolayer graphene showed greater catalytic efficiency and long-term stability than did bare ZnO. Interestingly, we found the catalytic efficiency of the graphene-coated ZnO thin film to depend critically on the nature of the bottom ZnO layer; graphene transferred to a relatively rough, sputter-coated ZnO thin film showed rather poor catalytic degradation of the dye molecules while a smooth sol-gel-synthesized ZnO covered with monolayer graphene showed enhanced catalytic degradation. Based on a systematic investigation of the interface between graphene and ZnO thin films, we concluded the transparency of graphene to be critically dependent on its interface with a supporting substrate. Graphene supported on an atomically flat substrate was found to efficiently transmit the properties of the substrate, but graphene suspended on a substrate with a rough nanoscale topography was completely opaque to the substrate properties. Our experimental observations revealed the morphology of the substrate to be a key factor affecting the transparency of graphene, and should be taken into account in order to optimally apply graphene as a protector of catalytic thin films and a booster of their catalysis.

Here, we demonstrated the transparency of graphene to the atomic arrangement of a substrate surface, i.e., the "lattice transparency" of graphene, by using hydrothermally grown ZnO nanorods as a model system. The growth behaviors of ZnO nanocrystals on graphene-coated and uncoated substrates with various crystal structures were investigated. The atomic arrangements of the nucleating ZnO nanocrystals exhibited a close match with those of the respective substrates despite the substrates being bound to the other side of the graphene. By using first-principles calculations based on density functional theory, we confirmed the energetic favorability of the nucleating phase following the atomic arrangement of the substrate even with the graphene layer present in between. In addition to transmitting information about the atomic lattice of the substrate, graphene also protected its surface. This dual role enabled the hydrothermal growth of ZnO nanorods on a Cu substrate, which otherwise dissolved in the reaction conditions when graphene was absent.

Cu3Sn alloy nanocrystals are synthesized by sequential reduction of Cu and Sn precursors through a gradual increase of the reaction temperature. By transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), UV/Vis spectroscopy, and X-ray diffraction (XRD) analyses, the alloy formation mechanism of Cu3Sn nanocrystals has been studied. The incremental increase of the reaction temperature sequentially induces the reduction of Sn, the diffusion of Sn into the preformed Cu nanocrystals, resulting in the intermediate phase of Cu-Sn alloy nanocrystals, and then the formation of Cu3Sn alloy nanocrystals. We anticipate that the synthesis of Cu3Sn alloy nanocrystals encourages studies toward the synthesis of various alloy nanomaterials., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Organic nonvolatile resistive switching memory is developed via selective incorporation of fullerene derivatives, [6,6]-phenyl-C61 butyric acid methyl ester (PCBM), into the nanostructure of self-assembled poly(styrene-b-methyl methacrylate) (PS₁₀ -b-PMMA₁₃₀) diblock copolymer. PS₁₀ -b-PMMA₁₃₀ diblock copolymer provides a spatially ordered nanotemplate with a 10-nm PS nanosphere domain surrounded by a PMMA matrix. Spin casting of the blend solution of PS₁₀ -b-PMMA₁₃₀ and PCBM spontaneously forms smooth films without PCBM aggregation in which PCBM molecules are incorporated within a PS nanosphere domain of PS₁₀ -b-PMMA₁₃₀ nanostructure by preferential intermixing propensity of PCBM and PS. Based on the well-defined PS₁₀-b-PMMA ₁₃₀/PCBM nanostructure, resistive random access memory (ReRAM) exhibits significantly improved bipolar-switching behavior with stable and reproducible properties at low operating voltages (RESET at 1.3 V and SET at -1.5 V) under ambient conditions. Finally, flexible memory devices are achieved using a nanostructured PS₁₀ -b-PMMA₁₃₀ /PCBM composite in which no significant degradation of electrical properties is observed before and after bending., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The cross-linking reaction of a TiO(2)-polymer composite (TPC) dielectric with poly(4-vinyl phenol) (PVP), a TiO(2) precursor, and poly(melamine-co-formaldehyde) is demonstrated: We suggest that the dense chemical structure of TPC is caused by the alkoxyl group of the PVP cross-linker, poly(melamine-co-formaldehyde) methylated/butylated, reacted with the hydroxyl group of the PVP and the ligands of the TiO(2) precursor.

Long-term stability of intermediate liquid crystal pretilt angles on a poly(dimethylsiloxane) (PDMS) ultrathin film grafted onto a surface was realized simply and easily via low-energy ion beam (IB) treatment. The composition and surface energy of the thin film could be controlled by varying the low-energy IB treatment. This treatment results in the permanent chemical modification of the film surface, converting it from organic PDMS to a mixed layer of organic PDMS and inorganic silica. The partial transformation of a PDMS surface gives rise to the control of the pretilt angle via the formation of the inhomogeneous surface and the stabilization of the pretilt angle via the cross-linking reaction of broken chemical bonds through IB irradiation. As a result, a continuous variation of pretilt angles that maintained their initial value with long-term stability was obtained. Thus, the unique chemical transformation of the PDMS surface using IB treatment may allow for the production of durable intermediate liquid crystal pretilt angles.